Electronic timepiece

ABSTRACT

An electronic timepiece having a magnetic circuit including permanent magnets mounted on an oscillator, said magnetic circuit including an air gap. A driving and controlling device including at least one coil is pivotably mounted in said timepiece for displacement in a plane extending substantially parallel to the oscillating direction of said oscillator between an operative position at which said coil is positioned in said air gap and an inoperative position at which said driving and controlling device is positioned out of overlapping relation with said oscillator. The oscillator may take the form of a balance wheel assembly formed of a pair of spaced balance wheels mounted in spaced relation on a common arbor, one of said balance wheels being formed of a magnetic material, the other of said balance wheels being formed of a non-magnetic material.

Kurita et al.

[ Dec. 25, 1973 ELECTRONIC TIMEPIECE [75] Inventors: Masahiro Kurita,Suwa; Tomio Ota,

Okaya, both of Japan [73] Assignee: Kabushiki Kaisha Suwa Seikosha,

Tokyo, Japan 221 Filed: Dec. 6, 1 971 [21] Appl. No.: 206,227

301 Foreign Application Priority Data 3,465,510 9/1969 .Ieanmonod 58/28R Primary ExaminerRichard B. Wilkinson Assistant Examiner-Edith SimmonsJackmon Attorney-Alex Friedman et al.

[ 5 7 ABSTRACT An electronic timepiece having a magnetic circuitincluding permanent magnets mounted on an oscillator, said magneticcircuit including an air gap. A driving and controlling device includingat least one coil is pivotably mounted in said timepiece fordisplacement in a plane extending substantially parallel to theoscillating direction of said oscillator between an operative positionat which said coilis positioned in said air gap and an inoperativeposition at which said driving and controlling device is positioned outof overlapping relation with said oscillator. The oscillator may takethe form of a balance wheel assembly formed of a pair of spaced balancewheels mounted in spaced relation on a common arbor, one of said balancewheels being formed of a magnetic material, the other of said balancewheels being formed of a non-magnetic material.

1 Claim, 9 Drawing Figures PATENTEDUECZS I975 3.780.521

sum 10? 6 PATENIEB DEC 25 I975 SHEET 3 BF 6 VPATENTEDUECZS ms 3,7852;

SHEET 8 OF 6 ELECTRONIC TIMEPIECE BACKGROUND OF THE INVENTION Thisinvention relates to electric timepieces incorporating oscillatorsformed with magnetic circuits which are controlled and driven by meansof fixed coils and driving circuits mounted relative to said oscillatormagnetic circuit. Further, this application relates to a specificconstruction for a balance wheel type oscillator.

In timepieces of the above-described type, the mounting or removal ofthe balance wheel or other oscillator required the removal of the blockscarrying the driving and detecting coils,.as well as the blocks carryingthe electronic circuitry associated with said coils. Since the gapbetween said coils and the permanent magnets mounted on the oscillatorand forming a part of said magnetic circuit is extremely small,mechanical contact, between said coils and balance wheel resulted fromsuch mounting and removal operations. This mechanical contact causedinterruption in the coil frequency, requiring resetting of the watch,and increasing the cost of repairing 'the watch.

Where said oscillator is formed of a balance wheel, further difficultieswere caused by the specific construction of the balance wheel. In smalltimepieces, such as wrist watches, when the balance wheel is formed of anon-magnetic material stray flux leaks from the permanent magnetsmounted thereon to produce highly disadvantageous effects includingsubstantial position errors. Further, in such constructions, other partsof the watch formed of magnetic materials, such as screws, wheels, thebalance arbor and the hair spring, cause adverse magnetic influences oneach other, which results in variations in the rate of the watch. On theother hand, a'balance wheel made of a material having high saturationmagnetic flux density and high permeability is usually soft and tends towarp. In such a construction, positioning of the balance wheel isdifficult. In an attempt to cure these difficulties, it has beenproposed to provide a balance wheel formed of non-magnetic material,material having a high saturation magnetic flux density and highpermeability being mounted on said balance wheel to define a part of themagnetic circuit. This construction further increases the thickness ofthe balance, as well as its weight and power consumption, and alsoresults in position errors.

SUMMARY OF THE INVENTION Generally speaking, in accordance with theinvention, an electronic timepiece is provided having oscillator meansincluding magnetic circuit means, said magnetic circuit means beingformed to define an air gap; driving and controlling means including atleast one .icoil means; and means for pivotably mounting said drivingand controlling means in said timepiece for pivotable displacement alonga plane extending substantially parallel to the oscillating direction ofsaid oscillator means between an operative position at which said coilmeans is positioned at least in part in said air gap and aninoperativeposition at which said driving and controlling means is positioned outof overlapping relation with said oscillator means. Said oscillator mayconstitute abalance wheel having permanent magnets mounted thereon anddefining said air gap therebetween, or said oscillator may comprise atuning fork. Said timepiece may incorporate a balance wheel assemblyhaving a pair of balance wheels mounted in spaced relation on a commonarbor, one of said pairof balance wheels being formed ofmagnetic'material, the other of said pair of balance wheels being formedof a non-magnetic material. A pair of permanent magnets is mounted oneach of said balance wheels, said pairs of permanent magnets being infacing relation and of a polarity to define a magnetic circuit includingthe air gap between said permanent magnet. A plate of magnetic materialis mounted on the outer surface of the balance wheel formed ofnon-magnetic material in the region between the pair of permanentmagnets mounted thereon, said plate forming a part of said magneticcircuit.

Accordingly, it is an object of this invention to provide an electronictimepiece wherein the oscillator may be readily removed and mountedwithout effecting the frequency of the driving'and controlling devices.

A further object of the arrangement according to the invention is toprovide a balance wheel constructionfor such electronic timepieces whichis regulateable, without providing the disadvantages of flux leakage and;positional error.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification anddrawings.

The invention accordingly comprises the features of construction,combinations of elements, and arrangement of parts which will beexemplifiedin the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of theinvention, reference is bad to the following description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a top plan view of one embodimentof the electronic timepieceaccording to the invention;

FIG. 2 is a partial cross sectional view of the electronic timepiece ofFIG. 1;

FIG. 3a is a top plan view of the balance wheel of the electronictimepiece of FIG. 1;

FIG. 3b is a side elevational view of the balance wheel of FIG. 3a;

FIG. 4 is a top plan elevational view of a second embodiment of theelectronic timepiece according to the invention;

FIG. 5 is a top plan view of a third embodiment of the electronictimepiece according to the invention;

FIG. 6 is a sectional view of the balance wheel assembly according tothe invention; and

FIGS. '7 and 8 are sectional views taken along lines 7-7 and 8-8respectively of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to FIGS. 3a and3b, the balance wheel assembly 7 consists of an upper balance wheel 2and a .lower balance wheel 3 mounted in spaced relation on a commonbalance wheel arbor 1. Fixed to upper balance wheel 2 are a pair ofpermanentmagnets 2a and 2b. A corresponding pair of permanent magnets 3aand wheel 2 interconnecting permanent magnets 2a and 2b while a lowermagnetic plate 5 is mounted on lower balance wheel 3 interconnectingpermanent magnets 3a and 3b. Said magnetic plates are formed of a highpermeability material. A hair spring 6 is fixed to arbor 1 for thenatural oscillation of balance wheel assembly 7. Electro-magnetic energyis applied to balance wheel 7 by an electronic circuit 8 moreparticularly shown in FIGS. 1 and 2, in order to maintain said balancewheel assembly in isochromatic oscillation.

As more particularly shown in FIGS. 1 and 2, said electromagnetic forceis applied to the balance wheel in a conventional manner by means of adetectingdriving coil 9 connecting with the electronic circuit 8 andheld in the gap intermediate permanent magnets 2a and 2b and permanentmagnets 3a and 3b. There is no mechanical contact between said coil andsaid permanent magnets. The relative motion between said permanentmagnets during the oscillation of balance wheel assembly 7 anddetecting-driving coil 9 induces a voltage in said coil which is appliedto electronic circuit 8 and controlled by an active elenent in saidelectronic circuit. In response to said induced voltage, the electricalenergy of battery 10 is applied to said detectingdriving coil tomaintain the oscillatory displacement of said balance wheel assembly.

Electronic circuit 8 and detecting-driving coil 9 are mounted as a uniton electric block 11, which is fixed to base plate 17 by means ofsetting screws l2, 13, 14 and 15. In this manner, the relative positionbetween the detecting-driving coil and the permanent magnet ismaintained during the operation of the timepiece. If setting screws 12,13 and 14 are removed, setting screw 15 is loosened, and battery 10 isremoved, electric block 11 may be pivotably rotated about the axisdefined by setting screw 15 from the operative position to I aninoperative position shown by dashed lines 11. This rotation is in aplane extending substantially parallel to the plane of oscillation ofthe balance wheel assembly so that the electric block 11 is out ofoverlapping relation with the balance wheel assembly after suchdisplacement. During such displacement, there is no engagement betweenany portion of the balance wheel assembly and any portion of theelectric block 11. When the electric block 1 l is positioned as shown inphantom lines in FIG. 1, balance wheel assembly 7 can be readily mountedand removed. In addition, the adjustment, conformation, mounting andremoval of escapement 16, which is positioned beneath balance wheelassembly 7 is readily achieved.

Referring now to FIG. 4, a second embodiment of the electronic timepieceaccording to the invention is depicted, said embodiment incorporating atuning fork as the oscillator. In said embodiment, detecting-drivingcoil 21 is mounted and maintained in the gap in magnetic circuits 28 and29 mounted on tuning fork oscillator 22. Magnetic circuits 28 and 29include permanent magnets 23 and 24 respectively and are attached to theend of the tines of said .tuning fork. Detecting-driving coil 21 isconnected'to an electronic circuit 25, said electronic circuit and coilbeing mounted in a common electric block 26.

Electric block 26 may be released by removing settated, the electricblock 26 assumes the position shown in phantom lines at referencenumeral 26', at which position the tuning fork may be readily removed.

A third embodiment of the electronic timepiece according to theinvention is depicted in FIG. 5, wherein the timepiece incorporates acontact point construction between an electrical contact mounted on thebalance wheel and a fixed spring contact for opening and closing thedriving circuit, associated with the driving coil. In the embodiment ofFIG. 5, balance wheel assembly 59 is similar in construction to thebalance wheel assembly depicted in FIG. 3, being provided with two pairsof permanent magnets and a pair of spaced balance wheels, of whichpermanent magnets 52a and 52b and balance wheel 52 is depicted in FIG.5.

A coil 51 is mounted in the gap between said permanent magnets in thesame manner as the coil shown in F IG. 2. This coil is fixed to anelectric block 55 which also carries a contact point spring 54. Saidelectric block is fixed by means of setting screws 56, 57 and 58. Whensetting screws 57 and 58 are removed. setting screw 56 is loosened andbattery 50 is removed, electric block 55 may rotate in the counterclockwise direction as viewed in FIG. 5 to a position shown in phantomlines at reference numeral 55'. Said rotation is about the axis definedby setting screw 56 in the direction of a plane extending substantiallyparallel to the plane of oscillation of balance wheel assembly 59. Thisarrangement not only permits the removal and mounting of the balancewheel assembly, but also permits the removal and mounting of the contactpoint spring 54 and the coil 51.

Referring now to FIGS. 6-8, a second embodiment of the balance wheelaccording to the invention is depicted. In said embodiment, the balancewheel assembly consists of a arbor 121 on which balance wheels 122 and123 are mounted in parallel spaced relation. Balance wheel 122 isprovided with a pair of permanent magnets 127 and 128 while balancewheel 123 is provided with a pair of permanent magnets 129 and 130.Permanent magnets 127 and 128 are in facing spaced relation withpermanent magnets 129 and 130 respectively. Balance wheel 123 is formedof a material having a high saturation magnetic flux density and highpermeability while balance wheel 122 is formed of a non-magneticmaterial and has a magnetic plate 124 of magnetic material attached onthe outer surface thereof in the region between permanent magnets 127and 128. Thus, the magnetic circuit includes the two pairs of permanentmagnets, magnetic plate 124 and balance wheel 123.

Each of the balance wheels 122 and 123 are provided with a counterweight and 126 respectively in order to compensate for the unbalancecaused by the mounting of said permanent magnets thereon. Adetecting-driving coil or coils 131 is provided in the air gap betweensaid permanent magnets and is connected to an electric circuitincorporating an active element such as a transistor for driving saidbalance wheel assembly.

A regulating'lever 132 is mounted within the timepiece for regulatingthe balance wheel. Said lever occupies the position indicator in phantomlines by reference numeral 132' when it regulates said balance wheelassembly. Since balance wheel 122 is formed of a nonmagnetic material,regulation may be accomplished without deformation thereof. A shieldmember may be provided near balance wheel 123 in order to eliminatestray fluxes caused by said balance wheel.

The balance wheel assembly of FIGS. 6-8 is extremely thin and operateswith high precision, and is particularly adapted for application towrist watches.

it will thus be seen that the objects set forth above, and those madeapparentfrom the preceding description, are efficiently attained and,since certain changes may be made in the above constructions withoutdeparting from the spirit and scope of the invention, it is intendedthat all matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

What is claimed is:

1. An electronic timepiece comprising a balance wheel assembly includingmagnetic circuit means, said magnetic circuit means being formed todefine an air gap; driving and controlling circuit means including atleast one coil means and other circuit components for driving andcontrolling the mechanical oscillations of said assembly; support meanscarrying at least portions of said driving and controlling circuit meansincluding said coil means and a plurality of said other circuitcomponents; means for pivotably mounting said support means in saidtimepiece for pivotable displacement along a plane extendingsubstantially parallel to the oscillating direction of said assemblybetween an operative position at which said coil means is positioned atleast in part in said air gap and an inoperative position at which saiddriving and controlling means is positioned out of overlapping relationwith said assembly; battery means electrically coupled to said drivingand controlling circuit means but mounted separate therefrom whereinsaid assembly includes an arbor; a pair of balance wheels mounted inspaced relation on said arbor for oscillation therewith as a unit; afirst of said balance wheels being formed of a non-magnetic material,the second of said balance wheels being formed of a magnetic material;first and second pairs of permanent magnets mounted in spaced facingrelation on said first and second wheels respectively; and a plateformed of magnetic material mounted on the outer face of said firstbalance wheel in the region overlapping and intermediate said first pairof permanent magnets, said permanent magnets being of a polarity todefine a magnetic circuit including said plate and said second balancewheel.

1. An electronic timepiece comprising a balance wheel assembly includingmagnetic circuit means, said magnetic circuit means being formed todefine an air gap; driving and controlling circuit means including atleast one coil means and other circuit components for driving andcontrolling the mechanical oscillations of said assembly; support meanscarrying at least portions of said driving and controlling circuit meansincluding said coil means and a plurality of said other circuitcomponents; means for pivotably mounting said support means in saidtimepiece for pivotable displacement along a plane extendingsubstantially parallel to the oscillating direction of said assemblybetween an operative position at which said coil means is positioned atleast in part in said air gap and an inoperative position at which saiddriving and controlling means is positioned out of overlapping relationwith said assembly; battery means electrically coupled to said drivingand controlling circuit means but mounted separate therefrom whereinsaid assembly includes an arbor; a pair of balance wheels mounted inspaced relation on said arbor for oscillation therewith as a unit; afirst of said balance wheels being formed of a non-magnetic material,the second of said balance wheels being formed of a magnetic material;first and second pairs of permanent magnets mounted in spaced facingrelation on said first and second wheels respectively; and a plateformed of magnetic material mounted on the outer face of said firstbalance wheel in the region overlapping and intermediate said first pairof permanent magnets, said permanent magnets being of a polarity todefine a magnetic circuit including said plate and said second balancewheel.